Git commits in Moodle 3.1.x by Jonathan Champ

commit e3d53b99aa18b60ca1ac3a9451c36ec3d7c5e78b
Author: Jonathan Champ <jonathan_champ@ncsu.edu>
Date:   Sat, 17 Dec 2016 01:20:45 +0800
Tag:    v3.1.5

MDL-57427 cache: Use perfdebug only when enabled

commit ddf98ccac392863b8d58d557846cb7ed1b27c89f
Author: Jonathan Champ <jrchamp@ncsu.edu>
Date:   Thu, 03 Mar 2016 12:33:15 +0800
Tag:    v3.1.0-beta

MDL-39524 setuplib: Improve get_real_size() performance and readability